Radiation detector direction

Abstract

A method for detecting the angle of arrival at a receiver of ionizing radiation from a source of unknown specific activity at an unknown distance by using an active filter between the detector and source that varies the intensity of the radiation by a predetermine factor according to position and then comparing that value to an unshielded detector's value forming a geometric ratio to determine the angle of arrival of the radiation at the receiver in relation to a predetermined reference plane or line.

I claim: 
     
       1. A method for detecting the angle of arrival at a receiver of ionizing radiation from a source of unknown specific activity at unknown distance from the receiver comprising providing at the receiver a detector responsive to said ionizing radiation, providing between the source and the detector a filter active upon the radiation to vary by a predetermined factor the intensity of radiation passing therethrough to the detector such that the detector provides an indication of a first intensity value, the filter being constructed such that the factor varies in dependence upon the position at which radiation incident upon the detector passes through the filter on its path to the detector, obtaining information concerning the intensity of the radiation independently by means of a second detector separate from said filter such that the radiation impinges upon said second detector without passing through said filter to provide a second intensity value and such that the second intensity value of radiation detected by the second detector is independent of the angle of arrival of the radiation and comparing said first and second intensity values as a geometric ratio to determine the angle of arrival of the radiation at the receiver in relation to a predetermined reference plane or line. 
     
     
       2. A method according to claim 1 wherein the filter is shaped such that intensity of the radiation passing threrethrough varies in accordance with a predetermined factor from a first position `theta`=0 (spherical coordinates) through an increasing angle from a central axis such that all positions lying upon a cone with its axis co-axial with the axis of the filter and its vertex coincident with the detector location therein, have the same factor. 
     
     
       3. A method according to claim 1 wherein the filter is shaped such that the intensity of the radiation passing therethrough varies in accordance with a predetermined factor from a first position `phi`=0 (spherical coordinates) through an increasing angle up to 180 degrees and varies in the same way on the opposite side of the filter between 360 degrees to 180 degrees providing a filter with its thickest point at 180 degrees symmetrical about a plane through the 0 and 180 degree positions and containing the axis. 
     
     
       4. A method for detecting the angle of arrival at a receiver of ionizing radiation from a source of unknown specific activity at unknown distance from the receiver comprising providing at the receiver a detector responsive to said ionizing radiation, providing between the source and the detector a filter active upon the radiation to vary by a predetermined factor the intensity of radiation passing therethrough to the detector such that the detector provides an indication of a first intensity value, the filter being constructed such that the factor varies in dependence upon the position at which radiation incident upon the detector passes through the filter on its path to the detector, obtaining information concerning the intensity of the radiation independently by means of a second detector separate from said filter such that the radiation impinges upon said second detector without passing through said filter to provide a second intensity value and such that the second intensity value of radiation detected by the second detector is independent of the angle of arrival of the radiation and comparing said first and second intensity values as a geometric ratio to determine the angle of arrival of the radiation at the receiver in relation to a predetermined reference plane or line, wherein the filter is shaped such that the intensity of the radiation passing therethrough varies in accordance with a predetermined factor from a first position `phi`=0 (spherical coordinates) through an increasing angle up to 360 degrees from said first position around a central axis. 
     
     
       5. A method for detecting the angle of arrival at a receiver of ionizing radiation from a source of unknown specific activity at unknown distance from the receiver comprising providing at the receiver a detector responsive to said ionizing radiation, providing between the source and the detector a filter active upon the radiation to vary by a predetermined factor the intensity of radiation passing therethrough to the detector such that the detector provides an indication of a first intensity value, the filter being constructed such that the factor varies in dependence upon the position at which radiation incident upon the detector passes through the filter on its path to the detector, obtaining information concerning the intensity of the radiation independently by means of a second detector separate from said filter such that the radiation impinges upon said second detector without passing through said filter to provide a second intensity value and such that the second intensity value of radiation detected by the second detector is independent of the angle of arrival of the radiation and comparing said first and second intensity values as a geometric ratio to determine the angle of arrival of the radiation at the receiver in relation to a predetermined reference plane or line, wherein the filter comprises a cone angle filter including a substantially spherical internal surface and an external surface which increases in radius proportionally to the "cone angle" and which is substantially spiral in shape with the detector positioned inside said inner surface, the centre of the sphere coincident with the detector location and lying on the central axis of the filter, and the filter being symmetrical about its axis such that any cross sectional view in a plane perpendicular to the axis will show the inner and outer surfaces as concentric circles and a second filter shaped such that the predetermined factor varies in dependence upon an increase in angle between two planes, one of which is the reference plane, and the other passing through the source of radiation, both of which intersect along the axis of the filter and both of which are perpendicular to a plane perpendicular to the axis, the internal surface of the filter being substantially spherical and the external surface being shaped such that any cross sectional view in a plane perpendicular to the axis shows the external surface as an arc of a spiral with the polar equation r = a θ and the internal surface as a circle, and any cross sectional view in a plane containing the axis shows the inner and outer surfaces as arcs of concentric circles, adjacent to both filters having their axis in the vertical position, providing the location of a line coincident with the propagation path of the radiation by identifying two angular measurements corresponding to the orthogonal system of spherical co-ordinates, which place the source of radiation along a directed line, the radius vector, passing through the receiver.